This invention relates generally to apparatus and methods for the production line testing of microwave oven cavities for microwave leakage.
Microwave oven cavities are typically fabricated from sheet metal formed to define a cavity enclosure and its accompanying microwave launcher section for housing the magnetron probe and waveguide section for coupling microwave energy from the launcher section to the interior of the cavity. Sheet metal joints are formed during fabrication by spot or projection welding or metal crimping techniques. A substantial number of such joints are typically formed in the fabrication process. A faulty joint may result in a flaw in the cavity which permits microwave leakage to the exterior of the cavity in excess of acceptable limits. Common practice today is to check the oven for leakage after manufacturing has been completed. At this stage the cavity has received several coats of paint, the door has been attached, all the components of the oven have been installed, and the outer oven housing and decorative trim has been applied. In the event a leak is detected at this stage the entire oven has to be torn down to allow manual correction of a faulty joint. To correct a weld, paint needs to be removed from the area of the defective weld of the cavity. Repainting is required once the correction has been made. All of these factors result in a lower production efficiency and increased production costs.
In view of the costs and loss of time associated with the repair of a defective joint detected after the completion of the oven assembly process, it would be desirable to provide a method and apparatus for testing the integrity of the cavity after the cavity and joint forming operations are complete but prior to the paint spray operation and subsequent oven fabrication steps.
It is therefore a primary object of the present invention to provide apparatus for accurately and rapidly performing leakage testing on oven cavities at that stage of the production line after the cavity and joint forming steps and before the subsequent fabrication steps.
It is a further object of the present invention to provide apparatus for exciting the cavity by a power source effectively internal to the cavity and monitoring radiation external of the cavity prior to mounting of the door and further assembly of the oven.